Mechanism of feldspar weathering—II. Observations of feldspars from soils

摘要: Examination of the surface morphology (via scanning electron microscopy) and composition X-ray photoelectron spectroscopy) sodic plagioclase potash feldspar grains taken from four different soils, provides little or no evidence for existence a tightly adhering protective layer altered on surface. Grains, which all clay has been removed by ultrasonic cleaning, exhibit same chemical in outermost few tens angstroms as underlying feldspar. Aluminum-rich ‘clay’ coatings continue to adhere after treatment are patchy, highly hydrous, unlikely act major diffusion-limiting, thus protective, barriers. Attack dissolution is non-uniform follows definite etching sequence characterized development growth distinctive etch pits. This can be reproduced treating fresh feldspars laboratory with strong HF-H2SO4− solutions and, thus, unaffected attacking solution. All our results suggest that during weathering controlled selective reaction at feldspar-solution interface not uniform diffusion through layer.